The present invention relates generally to temperature control systems for air conditioning units, including multiple mode air conditioning units, and, more particularly, to systems and methods for selectively remotely altering a locally-determined temperature setting through either auxiliary temperature set or auxiliary temperature set-back capability. The invention further relates to modular addition of such capabilities to existing thermostatic control systems with minimal design change.
A common configuration for a building heating and cooling system employs an individual air conditioning in each room of a hotel, office building or the like, with individual room thermostatic and mode selection control. Such a system desirably facilitates zoned operational mode and temperature control. That is, the operational mode and temperature of each room unit may individually be adjusted as desired.
In some such installations including a plurality of air conditioning units, central desk control stations have been provided for remotely controlling operational mode and temperature for energy conservation features. As will be appreciated, the ability to remotely control zone units is a desirable feature which permits overall economy of operation where not all rooms are occupied or in use at the same time. Unneeded units may either simply by turned off, or have the locally selected temperature setting varied. There are various circumstances in which it is desirable to permit the temperature of an unoccupied, or even an occupied, room to deviate from a nominal temperature. For example, in cold weather it may be desired to permit the temperature to drop somewhat, and in warm weather to let the temperature increase somewhat.
To these ends, various forms of remote or auxiliary temperature set-back, remote temperature set, and remote mode control capability have been proposed. For example, central desk control systems providing remote control of both mode and temperature are disclosed in Pratt, Jr. U.S. Pat. No. 4,174,064 and in Dawson U.S. Pat. No. 4,284,126. Central systems for remotely controlling temperature are disclosed in Bradford U.S. Pat. No. 4,077,566 and in Cleary et al U.S. Pat. No. 4,132,355. A system for introducing "false heat" to provide appropriate set back for heating and cooling is disclosed in O'Connor U.S. Pat. No. 3,386,496. Central systems for remotely controlling mode are disclosed in commonly-assigned Pohl et al U.S. Pat. No. 4,287,939 and in commonly-assigned Sidebottom U.S. Patent application Ser. No. 365,764 filed Apr. 5, 1982. Hoffman et al U.S. Pat. No. 4,060,123 discloses a form of auxiliary temperature control system wherein power to a room air conditioning unit is selectively interrupted during a low-energy mode to thermostatically maintain an alternative temperature when the room is not occupied.
In recent years, a variety of thermostatic control circuits which are electronic in nature have been developed. Such electronic thermostatic control systems typically include a voltage comparator having a comparison input and a reference input. A typical comparator is an integrated circuit device specifically adapted for voltage comparison. The output of the comparator is connected, usually through additional signal conditioning and logic circuitry, to control and energization of a thermal conditioning element such as a heater or refrigeration producer. A voltage comparator functions to produce the control output signal for energizing the thermal conditioning element when the comparison and reference inputs have a predetermined relationship to each other, for example, one being more positive than the other.
Connected to the comparator comparison input in a typical circuit is a temperature responsive voltage source comprising, for example, a thermistor included in a resistive network arrangement such as a voltage divider. Connected to the reference input is a reference voltage source providing a user-adjustable reference voltage for establishing a temperature setting. Thus, the reference input voltage establishes a switching threshold, and switching of the comparator output from one logic state to the other occurs as the comparison input voltage crosses the switching threshold. With appropriate connections, taking into account voltage polarities and logic sense, the thermal conditioning element cycles on and off as required to maintain the user-set temperature.
In one variation, the reference voltage source is fixed, and the user temperature setting control varies the characteristics of the thermistor voltage divider, which may comprise a thermistor and a variable resistance in series. The present invention is applicable to this variation as well.
Examples of this general type of comparator-based thermostatic-control circuit are disclosed in Wills U.S. Pat. No. 3,616,846, in Bailey U.S. Pat. No. 3,725,644, in commonly-assigned Pohl U.S. Pat. No. 4,290,481, and in commonly-assigned Alley et al application Ser. No. 151,855, filed May 21, 1980, now U.S. Pat. No. 4,346,755. The disclosure of this Alley et al U.S. Pat. No. 4,346,755 is of additional interest for its disclosure of a two-stage, comparator-based thermostatic control system wherein the temperature switching thresholds of two comparators are offset from each other to provide two stages of either heating or cooling.
When remote temperature setting or set-back capability is included in such a comparator-based thermostatic control system, there must be some means to selectively establish a new temperature set point (for a remote temperature set system) or to offset the user-determined temperature setting (for a remote temperature set-back system). These two functional concepts are similar, but differ in that remote temperature setting implies, ideally, absolute setting to a particular temperature regardless of the local temperature setting. Remote temperature set-back implies merely shifting the temperature set point a certain number of degrees relative to the locally set temperature. Several approaches toward achieving these ends have been proposed in the prior art. A typical approach involves a single-pole, double-throw switching arrangement which alternately selects one circuit element (or subcircuit) or the other depending upon whether the individual unit is in a normal or a remote mode of operation.